(SAN FRANCISCO CHRONICLE) Washington — A voter-approved California law requiring that egg-laying hens be able to spread their wings has become a flash point in negotiations over the $1 trillion farm bill, as Congress considers a measure that could upend dozens of state laws, including California’s ban on foie gras and shark-fin soup.

Rep. Steve King, R-Iowa, who calls animal rights groups “the vegan lobby,” won approval of a provision in the House version of the farm bill that would ban states from imposing stricter regulations for any farm product sold in interstate commerce beyond what other states require.

His immediate target was California’s Proposition 2, passed by voters in 2008, which requires that cages for veal calves, pregnant sows and egg-laying hens allow the animals to lie down, stand up, fully extend their limbs and turn around freely. It is set to take effect in 2015.

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